I am parenting a 5yr old who received an ASD (autism spectrum disorder) dx at the age of three. The most difficult thing about figuring out what is going on is that you are dealing with a spectrum of disorders. Each of them has their own set of diagnostic criteria, and each symptom can and does vary in severity, sometimes from day to day. There are children in my son's autism classroom who have a dx of classic autism and have NO sensory issues, while our son has many.
Our child was ultimately dx with PDD-NOS. This is considered a part of the autism spectrum. He exibits some but not all of the diagnostic criteria for classic autism. It is also common for children with an ASD dx to have other dx as well.
My advice to parents with concerns is to track the behaviors that you are most worried about. At the same time document what is happening right before the behavior is exibited, what time of day it happens and in what environment. This can be helpful for whoever is evaluating the child because no child behaves exactly the same in every single situation or environment that they find themselves in. Prior to going in for our evaluation I completed the online survey at
Childbrain.com - Welcome and noted my reasons for every response. The developmental pedi. found this very helpful and it also prevented me from forgetting to mention something.